Polarization actuator

ABSTRACT

The present invention relates to an apparatus for influencing a light beam arrangement comprising a plurality of light beams ( 4 ) arranged alongside one another, wherein provision is made of at least one optical element ( 5, 15, 25 ) which is movable transversely with respect to the light beams and by which the light beams can be influenced if the light beams pass through the optical element, and which has at least one light-absorbing region ( 9, 19, 29 ), wherein the apparatus comprises a drive device for the optical element, a measuring device for detecting the light of the light beam and a control unit, wherein the control unit is designed such that the drive device is controlled in a manner dependent on the position of the light-absorbing region. Furthermore, the present invention also relates to a projection exposure apparatus for microlithography comprising a multi-mirror array, in Which the corresponding apparatus can be used, and to a method for operating the corresponding apparatus or the projection exposure apparatus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for influencing a lightbeam arrangement comprising a plurality of light beams arrangedalongside one another, and to a projection exposure apparatus formicrolithography comprising a multi-mirror array, which is illuminatedby a plurality of light beams. Furthermore, the present inventionrelates to a method for influencing a light beam arrangement comprisinga plurality of light beams arranged alongside one another, moreparticularly influencing with regard to changing the polarizationdirection.

2. Prior Art

Projection exposure apparatuses for microlithography are used forproducing structures having extremely small dimensions inmicroelectronics or in nanotechnology. Accordingly, it is necessary thatstructures can be imaged with extremely high accuracy. For this purpose,actuators often have to be used in projection exposure apparatuses formicrolithography in order to position specific components exactly.

One example is afforded in the case of an illumination unit in which amultiplicity of light beams arranged alongside one another in twodimensions are directed onto an array of micro mirrors of a multi-mirrorarray, which are likewise arranged alongside one anothertwo-dimensionally here, in order to shape a corresponding illuminationbeam. In an illumination unit of this type, the polarization directionof the individual light beams is intended to be altered. For thispurpose, polarizers, for example in the form of polarization rotatorplates, have to be positioned in the beam path of the light beamarrangement or in the beam paths of the individual light beams

Since the exact positioning of corresponding components in opticalapparatuses described above causes a high complexity and thus highcosts, there is a need to seek simple solutions for this purpose.

DISCLOSURE OF THE INVENTION Problem Addressed by the Invention

Therefore, the problem addressed by the present invention is that ofproviding a simple possibility for the positioning and arrangement ofoptical elements in a projection exposure apparatus for microlithographyand, more particularly, for the arrangement of an optical element forinfluencing a light beam arrangement comprising a plurality of lightbeams arranged alongside one another.

Technical Solution

Said problem is solved by means of an apparatus comprising the featuresof Claim 1, a projection exposure apparatus comprising the features ofClaim 6, and a method comprising the features of Claim 8. The dependentclaims relate to advantageous configurations.

The invention is based on the assumption that simple and at the sametime exact positioning of an optical element for influencing a lightbeam arrangement comprising a plurality of light beams arrangedalongside one another can be achieved by virtue of the fact that ameasuring device detects a change in intensity by virtue of alight-absorbing region arranged at the optical element, and thearrangement of the optical element can be controlled in this way.

Accordingly, an apparatus for influencing a light beam arrangement isproposed, in which provision is made of at least one optical elementwhich is movable transversely with respect to the light beams and whichhas at least one light-absorbing region. In this case, the arrangementof the light beams in the light beam arrangement can be not onlyalongside one another one-dimensionally, but alongside one anothertwo-dimensionally, Furthermore, light is understood to mean not onlylight in the visible wavelength range, but generally electromagneticradiation. By virtue of the movability of the optical elementtransversely with respect to the light beams, that is to saytransversely with respect to the beam. direction of the light beamarrangement, the optical element can be moved into the beam path of thelight beam arrangement or into individual beam paths of the light beamsin order to influence the corresponding light beams during transmissionthrough the optical element. If the optical element has alight-absorbing region according to the invention, then thelight-absorbing region gives rise to shading in the further beam path,which can be detected by a measuring device. Thus, the correspondinglocation of the light-absorbing region can be determined and the driveof the optical element can be correspondingly controlled by means of acontrol unit. The direct detection of the position of the opticalelement makes it possible to design the drive device for the opticalelement in a simple fashion and thus to keep low the complexity for theactuator for moving and positioning the optical element.

In particular, a plurality of optical elements can also be arranged onebehind another in the beam direction of the light beams, which aremovable individually or altogether. In the case of a common movement ofthe plurality of optical elements, a light-absorbing region on one ofthe optical elements suffices, whereas in the case of individualmovability of the optical elements, each of the optical elements shouldhave at least one light-absorbing region.

In this case, the light-absorbing regions can be arranged at the samelocation in each case at the individual optical elements or they candiffer in their position such that an overlap of the light-absorbingregions in the beam direction of the light beams does not occur in anyposition of the optical elements, that is to say that an overlap of thelight-absorbing regions in the beam direction of the light beams isavoided in the case of any combination of the possibilities for thearrangement of the optical elements in the beam path, A simpleidentification of the position of the individual optical elements ispossible as a result.

By virtue of the invention, a simple drive device, such as a steppermotor, for example, can be used for the exact positioning of the opticalelement.

The optical element can be, more particularly, a polarizer, preferablyin the form of a pole rotator plate, which is used in an illuminationunit of a projection exposure apparatus for setting the polarization oflight beams directed onto a multi-mirror array.

Accordingly, the apparatus according to the invention can be used, moreparticularly, in a projection exposure apparatus for microlithographycomprising a multi-mirror array, which is illuminated by a plurality oflight beams arranged alongside one another, wherein, in a pupil plane ofthe projection exposure apparatus, exactly one region in each case canbe assigned to a plurality of light beams. More particularly,corresponding regions in a. pupil plane can be assigned to the lightbeams which are intended to be influenced. Consequently, in the pupilplane provision can be made of a measuring device for measuring thelight intensity, as is provided. according to the invention in theapparatus for influencing a light beam arrangement. More particularly,it is also possible to use a measuring device which is already used forother purposes in the region of the pupil plane of a projection exposureapparatus. in this way, the outlay for the exact positioning of thepolarizers in an illumination unit of a projection exposure apparatuscan be reduced further.

BRIEF DESCRIPTION OF THE FIGURES

In the accompanying drawings, in a purely schematic manner,

FIG. 1 shows part of an illumination unit of a projection exposureapparatus;

FIG. 2 shows an illustration of a further embodiment of an illuminationunit of a projection exposure apparatus in a plan view similar to thatfrom FIG. 1;

FIG. 3 shows a view of the apparatus from FIG. 2 rotated twice by 90°(side view rotated by 90° in the direction of the incident light);

FIG. 4 shows an illustration similar to FIG. 3 with identification ofthe light-absorbing regions;

FIG. 5 shows an illustration of a pupil plane associated with theillumination unit shown in FIG. 4, with identification of the mutuallyassociated channels of the beam path and regions of the pupil plane;

FIG. 6 shows an illustration of a further embodiment of an illuminationunit of a projection exposure apparatus in accordance with theillustration in FIGS. 3 and 4 with identification of the light-absorbingregions; and

FIG. 7 shows an illustration of a pupil plane associated with theillumination unit in FIG. 6, with identification of the mutuallyassociated channels of the beam path and regions of the pupil plane,

EXEMPLARY EMBODIMENTS

Further advantages, characteristics and features of the presentinvention will become clear in the course of the following detaileddescription of exemplary embodiments of the invention with reference tothe accompanying drawings.

FIG. 1 shows part of an illumination unit of a projection exposureapparatus for microlithography, in which incident light 1 impinges on aso-called focussing array 2, that is to say an array of focussing lenses3 arranged alongside one another and one behind another, in order to beconverted into a corresponding beam arrangement composed of amultiplicity of light beams 4 arranged alongside one anothertwo-dimensionally. The minors 8 of the multi-mirror array form an arrayof mirrors 8 arranged alongside one another two-dimensionally. By meansof the mirrors 8 of the multi-mirror array 7, the light beams 4 can bedeflected in the desired manner, in order to shape a light beam that isthen used for the illumination of a reticle of a microlithographyprojection exposure apparatus.

In an arrangement of this type, a polarizer in the form of apolarization rotator plate 5 is provided, which ensures that linearlypolarized light of the projection exposure apparatus can be altered byrotation of the polarization direction. The polarizer 5 can be broughtinto the beam path of the individual light beams 4 by means of a linearmovement transversely with respect to the light beams 4 or by means ofany other suitable movement, such as pivoting movements or the like, inorder to bring about a rotation of the polarization direction for lightbeams 4 which pass through said polarizer.

As is evident from FIG. 2, more particularly three polarizers 5, 15 and25 are arranged one behind another in the beam direction of the light 1,which polarizers can be moved into the beam path and removed againseparately and independently of one another,

FIG. 3 shows the arrangement of polarizers 5, 15 and 25 from the pointof view of the incident light 1, wherein the illustration hasadditionally been rotated by 90° about the light incidence direction.Accordingly, the polarizer 5, only half of which has moved into the beampath composed of the multiplicity of light beams 4 arranged alongsideone another, can be seen in the region of the lower half of FIG. 3,while the polarizer 15 that has moved somewhat further in can be seenabove the polarizer 5, and the polarizer 25 that has moved in the mostcan be seen above the polarizers 15 and 5 in FIG. 3. For the light beamsassigned to the individual mirrors 8 of the multi-mirror array, it ispossible to define fictitious channels 10 which are arranged alongsideone another two-dimensionally and through which the light beams pass.

Accordingly, in the case of a positioning of the polarizers 5, 15, 25 inaccordance with the illustration in FIG. 3, the light beams running inthe channels 10 of the two upper channel rows of the multi-mirror array7 would not be influenced in terms of their polarization direction,since they do not pass through any of the polarizers 5, 15 and 25. Thelight beams that pass through the horizontal rows Nos. 3 and 4 (countedfrom the top) of channels 10 pass through the polarizer 25 andexperience, for example, a rotation of the polarization direction by 45°through the polarization rotator plate of the polarizer 25.

The light beams that passes through the channels 10 of the row ofchannels arranged underneath passes not only through the polarizer 25but also through the polarizer 15, such that overall a rotation of thepolarization direction by 90° is effected even if the polarizer 15comprises a pole rotator plate that brings about a rotation by 45° inthe same direction as the polarizer 25.

Accordingly, the light beams that pass through the channels 10 in thelower three channel rows illustrated are influenced, for examplerotated, three times in their polarization direction as a result ofsuccessively passing through three polarizers, namely the polarizers 5,15 and 25.

As a result of the displacement of the polarizers 5, 15, 25, the lightbeams that pass through different channels 10 can then be influenced intheir polarization direction in a targeted manner. Accordingly, it isnecessary that the polarizers 5, 15, 25 can be positioned exactly,

For this purpose, the invention provides for the polarizers 5, 15, 25 tocomprise light-absorbing regions 9, 19, 29, for example in the form of adeposited. metal layer, such as, for example, chromium or the like, Inthe exemplary embodiment shown in FIG. 4, the light-absorbing regions 9,19, 29 are provided at the same location in each case at the polarizers5, 15, 25 namely at the top right corner of the pole rotator plates inthe exemplary embodiment shown.

As is evident from FIG. 5, a specific region 11 can be assigned to eachchannel 10 in the pupil. plane 12, which is identified by the samedesignation with upper-case letters A to H.

A measuring device can now be arranged in the pupil. plane 12, saidmeasuring device detecting the light intensity. Such a measuring devicemay, for example, already be provided for other purposes, too, in theprojection exposure apparatus and be concomitantly used for the presentinvention. By virtue of the light-absorbing regions 9, 19 and 29, whichare arranged in the region of the channels C, E and F, no or a lowerradiation intensity can be ascertained in the pupil plane 12 in theregions 11 identified by C, E and F, such that, by means of acorresponding control and/or evaluation unit, more particularly in theform of a data processing device which is set up accordingly in terms ofprogramming, it is possible to ascertain that the polarizers 5, 15, 25have to be positioned with their light-absorbing regions 9, 19, 29 incorresponding positions in the beam. path.

However, since the light-absorbing regions 9, 19, 29 of the polarizers5, 15, 25 are provided at in each case the same location of thepolarizer 5, 15, 25, from the measurement of the light intensity in thepupil plane 12 it is not possible directly to ascertain which polarizeris responsible for the covering of which region 11 in the pupil plane12. However, this can be determined during initial adjustment andsubsequent tracking of the movements of the polarizers 5, 15, 25.

Alternatively, the light-absorbing regions 9, 19, 29 of the polarizers5, 15, 25 arranged one behind another can be provided at differentlocations of the polarizers 5, 15, 25, as is shown for thelight-absorbing regions 9′, 19′, 29 in FIG. 6. While the light-absorbingregion 29 of the polarizer 25 is once again arranged at the top rightcorner of the pole rotator plate, as in the exemplary embodiment in FIG.4, the light-absorbing regions 9′ of the polarizer 5 and 19′ of thepolarizer 15 are arranged at other locations, to be precise moreparticularly in a region which is offset by at least one channel widthwith respect to the other light-absorbing regions of the remainingpolarizers.

Accordingly, the polarizer 5, in the case of an inward and outwardmovement, will cover with its light-absorbing region 9′ only thechannels 10 designated by the upper-case letter A to H, while thepolarizer 15 can cover with its light-absorbing region 19′ the channels10 having the designations A′ to H′ and the polarizer 25 can cover withits light-absorbing region 29 the channels 10 identified by A″ to H″.Accordingly, in the pupil plane, the shadings caused by thelight-absorbing regions 9′, 19′, 29 can be precisely separated from oneanother, since no overlap can take place, as is the case for example inthe exemplary embodiment in FIG. 5.

Accordingly, the position of the individual polarizers 5, 15 and 25 canbe determined by the detection of the light intensity in the pupil plane12 and the movement of the polarizers 5, 15 and 25 can be controlledaccordingly. if it is provided, for example, that the polarizer 5, asshown in FIG. 6, is intended to be moved into the beam path of the beamarrangement to an extent such that the beams that are guided through thelower three rows of channels 10 are intended to pass through thepolarizer 5, then the light-absorbing region 9′ is arranged in theregion of the channel 10 identified by the upper-case letter F. For thispurpose, the polarizer 5 is driven by a drive device, such as, forexample, a stepper motor or the like, to carry out a linear movementuntil the measuring device in the pupil plane 12 ascertains that theregion 11 identified by the upper-case letter F in FIG. 7 is now coveredby the light-absorbing region 9′, such that no or little light intensitycan be ascertained. Accordingly, the movement of the polarizer 5 canthen be stopped and the polarizer 5 is arranged in the correct position.As a result, it is possible to use a drive device of simple design, suchas a stepper motor, for example, for exact positioning of the polarizer5. The corresponding polarizers 15 and 25 are controlled and moved in asimilar way.

Although the present invention has been described in detail on the basisof the exemplary embodiments, it is self-evident to the person skilledin the art that the invention is not restricted to these exemplaryembodiments, rather that the invention can also be used in othercontexts and that modifications can be made in such a. way thatindividual features presented are omitted or different combinations offeatures presented are realized, as long as there is no departure fromthe scope of protection of the appended claims. In particular, thepresent disclosure includes all combinations of all features presentedindividually.

1. Apparatus for influencing a light beam arrangement comprising aplurality of light beams arranged alongside one another, characterizedby at least one optical element (5, 15, 25) which is movabletransversely with respect to the light beams (4) and by which the lightbeams can be influenced if the light beams (4) pass through the opticalelement (5, 15, 25), and which has at least one light-absorbing region(9, 19, 29), wherein the apparatus comprises a drive device for theoptical element, a measuring device for detecting the light of the lightbeams and a control unit, wherein the control unit is designed such thatthe drive device is controlled in a manner dependent on the position ofthe light-absorbing region.
 2. Apparatus according to claim 1,characterized in that a plurality of optical elements (5, 15, 25) arearranged one behind another in, the beam direction of the light beams,which are movable individually or altogether.
 3. Apparatus according toclaim 2, characterized in that the light-absorbing regions (9, 19, 29),in the case of a plurality of optical elements, are arranged at the samelocation in each case at the individual optical elements or are arrangedsuch that they do not overlap in any position of the optical elements inthe beam direction of the light beams.
 4. Apparatus according to any ofthe preceding claims, characterized in that the drive device is astepper motor.
 5. Apparatus according to any of the preceding claims,characterized in that the optical element (5, 15, 25) is a polarizer. 6.Projection exposure apparatus for microlithography comprising amulti-minor array (7), which is illuminated by a plurality of lightbeams (4), such that, in a pupil plane (12) of the projection exposureapparatus, a respective region (11) is assigned to a plurality of lightbeams (4), characterized in that the projection exposure apparatuscomprises an apparatus according to any of the preceding claims. 7.Projection exposure apparatus according to claim 6, characterized inthat the measuring device is formed by a device for measuring the lightintensity in the pupil plane (12).
 8. Method for influencing a lightbeam arrangement comprising a plurality of light beams (4), arrangedalongside one another, more particularly with an apparatus according toany of claims 1 to 5 or a projection exposure apparatus according toeither of claims 6 and 7, characterized by providing at least oneoptical element (5, 15, 25) which is movable transversely with respectto the light beams and by which the light beams (4) are influenced ifthe light beams pass through the optical. element, and which has atleast one light-absorbing region, providing a drive device for theoptical element, and providing a measuring device for detecting thelight of the light beams, wherein the optical element is driven in amanner dependent on the position of the light-absorbing region (9, 19,29) such that it assumes a position in which the desired light beams areinfluenced.